Frederick II of Austria

Frederick II "the Quarrelsome", Duke of Austria (25 April 1211-15 June 1246) was Duke of Austria from 1230 to 1246, succeeding Leopold VI of Austria and preceding Vladislaus III of Moravia. Frederick was the last ruler of Austria from the House of Babenberg, as he was killed in the Battle of the Leitha River with the Kingdom of Hungary in 1246.

Biography
Frederick was born on 25 April 1211, the second surviving son of Leopold VI of Austria and Theodora Angelina. The death of his older brother Henry in 1228 led to him becoming the only possible heir to the duchy of Austria and Styria, and he succeeded his father on his death in 1230. The young duke frequently fought against Hungary, Bohemia, and Bavaria, being nicknamed "the Quarrelsome" due to his habit of fighting against his neighbors (he was very proud of his Byzantine descent). He even had disputes with Emperor Frederick II of Germany, and Frederick allowed Wenceslaus I of Bohemia to invade Austria; Vienna allowed for Bohemian and Bavarian troops to enter the city in 1235. In 1237, Conrad IV of Germany was crowned King of the Romans in Vienna, which became a free imperial city. However, in 1239 he made amends with the emperor, and he began to support the Hohenstaufens in their disputes with other German nobles. This allowed him to focus on external affairs, claiming the western counties of Hungary. Frederick was slain at the Battle of the Leitha River while fighting Bela IV of Hungary's army, ending the Babenberg line and allowing for several other nobles to compete for power in Austria.